Cast nickel-base alloy for gas turbine rotors



Y temperature for relatively long periods of time.-

United States Patent Office f 3,166,412 Patented Jan. 19, 1965 3,166,412CAST NICKEL-BASE ALLY FOR GAS TURBINE ROTRS Clarence G. Bieber, RoseliePark, NJ., assigner to The International Nickel Company, Inc., New York,N.Y., a corporation of Delaware No Drawing. Filed Aug. 31,1962, Ser. No.220,857

4 Claims. (Cl. l5-171) in gas turbines employed in aircraft and in otherapplica-` tions. Generally, for aircraft applications, the nickelbasealloy bladesare produced individually and are ythen fastened into arotor'hub which is made of a d ilferent alloy to produce a compositeturbine rotor. Since the hub portion of the rotor is not required-tooperate `.at the very high temperatures to which theblade portions ofthe rotor are-subjected, the metal or alloy which is employed for therotor hub is required only to have good strength and ductility over thetemperature range from approximately room temperature upv to, possiblyl000 F. or

12009 F. ln the production ofturbine rotors for use in gas turbines ofrelativelyV small size which can be employed in automotive gas turbineapplications, the economic picture is quite different from the case ofaircraft gas turbines. economically feasible to produceithe bladesseparately and then fasten them to the rotor Ahub so as ,to form acomposite turbine rotor.

posed to produce` the turbine Vrotor as a unitary casting having theblades integrallycast into` the hub., Since the i blade portions oftherotor are subjected to completely different combinations of stressand temperature than is the hub portion ofthe rotor, a vexingmetallurgical prob-` rotors made of the4 special cast alloy provided inaccordance with the invention and which have the blades cast integrallywith the hub.

Other objects and advantages will become apparent from the followingdescription.

Generally speaking, the present invention provides cast nickel alloyscontaining, in percent by weight, not more than about 0.05% or 0.06%carbon, e.g., about 0.03% carbon, about to about 18% chromium, about 5%to about 7% aluminum, up to about 1.5% titanium, e.g., 0.5% to about1.5% titanium, about 1% to about 3% columbium, about 0.5% to about 6%molybdenum, with the chromium plus molybdenum contents being about toabout 20% of the alloy, up to about 0.05%

boron, up to about 0.15% zirconium, up to about 0.05%

calcium, andthe balance essentially nickel. For best combinations ofstrength and ductility, chromium advantageously is maintm'ned in therange of 10% to 14%. p

The total content of chromium and molybdenum in the alloy is import-antand must be maintained in the range of 15% to 20% in order to providethe best combination that which exists in Thus, it is no longer It hasaccordinglybeen pro- .of corrosion resistance, strength, and ductilityat elevated temperatures. Aluminum `is an important hardening andstrengthening element in the alloy and is maintained in the range of 5%to`7% because strength is`sacriticed if the concentration of thiselement is too low while the ductility is lowered if the concentrationis above 7%.

Titanium, when present even in amounts of about 0.5%, contributesfurther hardening and strengthening to the alloy but should not exceedabout 1.5% of the alloy because ductility and castability are reduced ifthe titanium content is higher than this value. Columbium also plays animportant part in strengthening thealloy and is' employed in amounts of1% to 3% because strength is sacrificed if Vthe concentration of thiselement is below 1%l while the ductility is reduced if the concentrationis above'3r%; Boron and zirconium present in the alloycontribute-markedly to the development of satisfactory lem iscrea-tedisince it is necessary to provide within a Y single unitarycasting metallurgical structures'which will operate under vastlydiiferent conditions of stress and temperature. It is known that alloyswhich are satisfactory forservice in the rotor hub blade materials. inpractice that the alloys which are satisfactory as the blade materialsare notfsatisfactory for use in the hub portion of the rotor,Accordingly, a demand has arisen for a nickel-base lcas'tingalloyhavingV properties which would render it at the same time satisfactoryfor use as a cast rotor hub material and for use as a cast turbine bladematerial. y

Although attempts havebeenmade to .overcome the foregoing dilicultiesand` other diiiieulties, none, as Vfar as I am aware, was entirelysuccessful when carried into practice'commercially on anindustrialscale. i

It hasnow been discovered that particular cast nickel#V Another objectofthe present invention is `to provide a cast alloy having highcombinationsV of strength and ductility at usual ambient temperatures.

The invention also contemplates providing gas turbinev areunsatisfactoryas OnV the other hand, it has been found' strength andductility properties therein.. Thus, the presence of fas little as0.005% boron and at least about `,0.02% zirconium provide goodductility-` at temperatures" ab'oveabout1000jo to 1200 F. Calcium inthealloy is employedin air melting to serve as a deoxidizer. It isomitted in vacuum melting.. VIt is to be understood that ,carbon inthe`alloymust be Vmaintained at very low vales not exceeding 0.06% in orderthat the alloys will exhibit the required high elongation inthe as-castcondition at room temperature even in sections as heavy as three inchesthick or more. Small carbon contents of about 0.03% arebeneiicial inproducing the master alloy Vwhich is tobe remeltfed to make the finishedcastings.

The alloy provided in accordance with the invention may also contain uptoV 15%` cobalt, e.g., about V10% cobalt, assuch amounts of cobaltpermit the inclusion in the alloy of as much as about 8% of aluminumwithout encounterling serious embrittling effects; vTungsten may beemployed in` placebf apart or all of the molybdenum in the Aalloy. ,"Thealloy should be as devoid as practicable of impurities such as sulfur,phosphorus, lead, antimony, tin, selenium, tellurium, bismuth, etc.Elements such as silicon and 'manganese are undesirable and should notbe present in amounts exceeding about 0.2% and 0.1%, respectively. 'Ironis also an undesirable element in the alloy `land should not be presentin amounts exceeding about 0.5%, e.g., about 0.25%. The balance of thealloy is essentially nickel.

The alloy provided in accordance with the invention is characterized bya room temperature'tensile strength -in the as-cast condition of atleast about 100,000 p.s.i. and anelongation of at least about 10% in.the Ias-cast condition. In addition, the alloy provides relatively longservice life at temperatures on the order of about 1700` F. to

The'following tables contain, respectively, the chemical :ompositions,in percent by Weight, of vacuum melted and vacuum cast alloys producedin accordance with the invention, the rupture lives of the alloys at17.00 F. and 30,000 p.s.i. in the as-cast condition, and the roomternperature tensile properties of these alloys in the `as-cast jconditionz- Table I Alloy Perler- Per- Per- Per- Per- Per- 'Per- Per-No. cent (eut cent cent ycent cent cent cent cent Cr Mo Cb A1 Ti C Zr NiL v ,12 5 2 6 0.6 0.008 0.01 0.10 .Bal Z 12 5 2' 6 0.6 0.05 0.01 0.10Bal.

Table Il y Y Rupture Life, v Y y f .Alloy No. Hours,-1700 F., PercentElongation v `30,000 psi.

1Q.' 57.2, 12:4 2 74.0 g l 24 Table III j Yield VUltimate Y Alloy No.Strength, Tensile `Percent',

f p.s.i. Strength, Elongation j Y 7 psi.

In contrast to the properties developed in the foregoing alloys, anotheralloy identical Vin composition to Alloy No.- 2 set forthhereinbeforeexcept that incontained 0.12% carbon was found to have a satisfactoryrupture life of 64 hours at 1700 Rand 30,000 p.s.i.ltogether Vention isparticularly applicable to the production of castings, such `as turbinerotors having the blades integrally cast with the hub, which have atleast one included section subjected in use to high stress attemperatures on the order of about 1700 F. andhave at least one includedsection subjected in use to high stress at temperatures on the order ofabout 1000o F. Such castingsproduced in accordance with the inventionprovide satisfactory properties although portions thereof `are subjectedto very different service `temperatures from those to which otherportions of the casting are subjected. The castings have improvedfatigue strength.

As Will be readily understood by those skilled iu the art', theexpression ,balance essentially nickel does not exclude the presence ofother elements commonly present in such alloys as incidental elements,eg., deoxidizing and cleansingelements, andirnpurities ordinarilyassociated therewith in small amounts which do not adversely affect thebasic characteristics of my alloys. p

VAlthough the present inventionhas been described in conjunction with.preferred embodiments, it is` to be understood rthat modifications andvariations may be, resort'edftov Without departing from the spirit andscope of the invention as those skilled in the art will readilyunderstand. Suchmodifications and variations are considered ,to bewithin the purview and scope of the invention and appendedclairns.. j

I claim: v f Y 1. A casting having atleast oneincluded sectionsubjectedin use to high stressat temperatures on the order of Vabout17009 F. and at least one included section subjected in use to highstress at temperatures on the order of about 1000* F., made of'anv alloyconsisting' essentially of vabout0.008% `to 0.05%fcarbo'n, aboutv 12%chromium, about '5% molybdenum, Vabout 6% aluminum, .about 0.6%titanium, -about 2%, columbiurn,` about 0.01%

with a room temperature vyield strength of 104,000 psi.

and a room temperature tensile strength of 126,000 psi. but was found tohave an elongation at room temperature j of yonly 6%. i' f fAlloys inaccorda ncewith the invention have particulalrly satisfactory propertieswhen produced byr vacuum Y melting'. They may, however, be melted underargon or even under air'atmospheres with goodcastability and j. f

with onlyslight sacrifice `in properties as compared tof those producedby vacuum melting.

The strength of the alloy at room temperature and atl i elevatedtemperatures may be improved by subjectingithe castings ,to a heattreatment comprising a heating at about j 215011?. for about 15 minutesto about'24'hours, e.g., about two hours, followed by acooling toroomtemperature. fjlffde'sired', a further stabilization treatmentconsisting of a heating at about 1700o F. for about one to about 24hours, -ie.g.,about fourV hours, kmay also be employed. .in castingthefalloy, it is important to superheat the, melt 'topa temperature of,at least 300 F., butk more-advantageously at least about 400 F; or 500F.,

e.g.,5600' F.,'about the 'freezingtemperature thereof. For example, apouring temperaturehvof about 2950 F. Y.

is very satisfactory.A

The yalloy provided in accordance w ith the present yin-` boron, about0.1% zirconium, and the balance essentially nickel. r` Y 2. Anickel-base al loy containing` not morey than about 0.06% carbon, about'10%.to 18% chromium, Vabout 0.5% to 6%V of a metal from the groupconsisting of molybdenum and tungsten andwith the total contents ofchromium, molybdenum andtung'sten being about 15 to about=20%, about 5%to 8% aluminum, up to about 15% cobalt with the proviso thatWheri'theicobalt content isv lessthanvabout 10% `the aluminum content isabout 5% to,7%, up to about 1.5% titanium, about 1% to 3% columbiurmabout 0.01% boron,V up ,toV about 0.15%

.0 5 %V calcium, and thevbalanc'e References Citedin the file of thispatent UNITED' STATESPATENTS y, Y 2,912,323 Bieber et a1. 1; 1 Nov. 10,1959 2,975,051Y vviisonetal.maman111111.14,1961 3,0o5;7e4. Fsu1imer;; roct. 24,1961

L I FOREIGN PATENTS 45218,77?, J Canada Y Nov. 12, 1957.

"loy according to claim 1 `vvherein i UNITED STATES PATENT OFFICECERTIFICATE 0F CORRECTION Patent No. 5,166,412 January 19, 1965 ClarenceG. Bieber It is hereby certified that error appears in the abovevnumbered patent requiring correction and that the said Letters Patentshould read as corrected below.

Column 3, line 65, for "about" read -above Signed and sealed this 6thday of July 1965e (SEAL) Attest:

Commissioner of Patents

2. A NICKEL-BASE ALLOY CONTAINING NOT MORE THAN ABOUT 0.06% CARBON,ABOUT 10% TO 18% CHROMIUM, ABOUT 0.5% TO 6% OF A METAL FROM THE GROUPCONSISTING OF MOLYBDENUM AND TUNGSTEN AND WITH THE TOTAL CONTENTS OFCHROMIUM, MOLYBDENUM AND TUNGSTEN BEGING ABOUT 15% TO ABOUT 20%, ABOUT5% TO 8% ALUMINUM, UP TO ABOUT 15% COBALT WITH THE PROVISO THAT WHEN THECOBALT CONTENT IS LESS THAN ABOUT 10% THE ALUMINUM CONTENT IS ABOUT 5%TO 7%, UP TO ABOUT 1.5% TITANIUM, ABOUT 1% TO 3% COLUMBIUM, ABOUT 0.01%BORON, UP TO ABOUT 0.15% ZIRCONIUM, UP TO ABOUT 0.05% CALCIUM, AND THEBALANCE ESSENTIALLY NICKEL.